I need to modify the xml config files in order to change the default sort in folder view (change it from alphabetical to directory order) as described in the server forum. Apparently i need to change the view-definitions.xml file however i cannot find this file on my MAC.

I don't have a Mac at my desk so I can't tell you the exact path, but I know the TwonkyServer .ini file is located in the User's directory under:
Library/Application Suppport/twonkyserver/twonkyserver.ini

You might want to check here, if you haven't already. If it's not there, please let me know and I'll get you an answer.